Attack by Stratagem · Complete Victory
Sun Tzŭ said: In the practical art of war, the best thing of all is to take the enemy's country whole and intact; to shatter and destroy it is not so good. So, too, it is better to capture an army entire than to destroy them. Hence to fight and conquer in all your battles is not supreme excellence; supreme excellence consists in breaking the enemy's resistance without fighting.
Taking the other side whole is better than smashing it. Winning every battle is not the highest skill; making the other side give in without a fight is.
Attack by Stratagem · Hierarchy of Attack
Thus the highest form of generalship is to baulk the enemy's plans; the next best is to prevent the junction of the enemy's forces; the next in order is to attack the enemy's army in the field; and the worst policy of all is to besiege walled cities. The general, unable to control his irritation, will launch his men to the assault like swarming ants, with the result that one-third of his men are slain, while the town still remains untaken. Such are the disastrous effects of a siege.
Best is to wreck the enemy's plans; next, break up his alliances; next, defeat his army; worst, besiege his cities. A siege takes months and costs lives, and is only for when there is no other way.